Win32:Trojan-gen

A virus named Win32:Trojan-gen is bothering me... I'm using AVAST, but it just keeps coming back! every time I turn on the computer AVAST warns me about this virus.... it is most of the times in the file ...WinTools\WToolsS.exe and WinTools\Update\WToolsS.exe and a few times it has been found in System Volume Information in A0003408.exe/A0003816.exe